libvlc: Advertise libvlc_media_instance_destroy_and_detach (soon media_instance_release) in the libvlc.h header.

"This is part of a former submission stripped out for easier
 assimilation. It modifies vout_subpictures to use the existing alignment
 field on each region, rather than the alignment on the subpicture plane
 itself. Modifications are made to everywhere that depended on the former
 behaviour, to make it use the new alignment location instead."

Fix invalid free crash in bookmarks loading code reported by Gids on IRC. Small test case is: (I'm not sure that it really needs to be that long)
#EXTVLCOPT:bookmarks={name=Rainforest Shmainforest,bytes=5276429,time=1},{name=Spontaneous Combustion,bytes=113071718,time=1331},{name=The Succubus,bytes=218546569,time=2663},{name=Jakovasaurs,bytes=326602991,time=3999},{name=Tweek Vs. Craig,bytes=436968699,time=5326},{name=Sexual Harassment Panda,bytes=542655194,time=6658}
episodes-1-6.m4v

libvlc: Rename input to media_instance. And add the possibility to create a medi_instance from a media_descriptor.

 - ogg/vorbis (close #125)
 - flac (and not ogg/flac yet)
 - mp3/aac (id3/ape)
 - mpc (internal/ape)

it, disabled by default)

Parse TXXX fields (id3)
Parse RVA2 and convert them to replay gain (id3)
(I cannot put APE parsing into a new module as id3 and ape can be found
in the same file, this means you need libid3tag)